Equipment for drying gas, in particular air, by refrigeration

ABSTRACT

The disclosed equipment provides for the flow of gas to be dried in a vertically downward direction through a precooling gas/gas heat exchanger and then in a vertically downward direction through a removable insert refrigerant cooling coil configuration of a gas/refrigerant heat exchanger for cooling. A filter removes impurities in the cooled gas extracted from the lower portion of the gas/refrigerant heat exchanger before it is recirculated through a removable insert pipe arrangement of the gas/gas heat exchanger. Such recirculation enables the cooled gas to precool newly admitted gas within the gas/gas heat exchanger. It also increases the temperature of the cooled gas by a prescribed magnitude before it is exhausted from the gas/gas heat exchanger for functional use.

United States Patent Zander et al.

[ Aug. 12, 1975 [54] EQUIPMENT FOR DRYING GAS, IN 3,129,077 4/1964 Adams165/143 X PARTICULAR AIR, BY REFRIGERATION 3,247,681 4/1966 Hankison eta1... 62/317 3,271,934 9/1966 Shields /269 Inven or rn Zander, ig; Bernt3,541,807 11 1970 Henderson 62/93 xf fil day a" FOREIGN PATENTS ORAPPLICATIONS of German), 1,202,252 8/1970 United Kingdom 55/269Assigneei VIA G s llschaft fur Primary ExaminerAlbert W. Davis, Jr.

Verfahrenstechmk, Dusseldorf Assistant ExaminerSheldon Richter GermanyAttorney, Agent, or Firm-Frederick W. Padden [22] Filed: June 21, 1973 3[57] ABSTRACT [21] Appl' 72333 The disclosed equipment provides for theflow of gas to be dried in a vertically downward direction through [30]Foreign Application Priority Data a precooling gas/ gas heat exchangerand then in a ver- July 1. 1972 Germany 2232386 tically downwarddirection through a removable insert refrigerant cooling'coilconfiguration of a gas/refriger- 52 us. (:1. 165/111; 55/269; 62/90; antheat exchanger for Cooling. A filter removes p 2 9 62/272; 1 5 165/178rities in the cooled gas extracted from the lower por- 51 Int. Cl F28b1/00; F28f 9/26 tion of the gzls/rfifrirmrdnt heat exchanger before itis [58] Field of Search 62/90, 93, 272, 317; recirculated through aremovable insert P p arrange- 165/I43, 163, 178 1 1 55/269 ment of thegas/gas heat exchanger. Such recirculation enables the cooled gas toprecool newly admitted gas 56 1 References Cited within the gas/gas heatexchanger. It also increases the UNITED STATES PATENTS temperature ofthe cooled gas by a prescribed magni- 2 2 7 332 1 B t l ff t I 6 tudebefore it is exhausted from the gas/gas heat ex- I re 7. a e a 2,655,34710 1953 Bielfeldt 55/269 changer for funct'onal 2,723,540 11/1955 Derr/144 4 Claims, 5 Drawing Figures Q (Q L 1 ,0 .o .o figs 4 w, 5 7/ I \Q:O i 0 i i o o 84 o o I 80 0 6O 0 l 8 2 o PATENTEU AUG 1 2 I975 SHEETPATENTED AUG 1 2 ms SHEET EQUIPMENT FOR DRYING GAS, IN PARTICULAR AIR,BY REFRIGERATION BACKGROUND OF THE INVENTION This invention relates toequipment for drying gas, such as air, by refrigeration and particularlyto an equipment arrangement in which a gas to be dried flowssuccessively through a gas/gas heat exchanger, a gas/refrigerantexchanger and subsequently again the gas/gas heat exchanger in acontinuous loop.

As is known, the principle of drying gas by refrigeration is based uponthe fact that the dew point of the gas to be dried is lowered so thathumidity contained in the gas is separated, along with at least aportion of further impurities. l-Ieretofore, in prior art devices fordrying gas by refrigeration the two heat exchanger columns arepositioned in a horizontal direction so that due to the use of twodifferent kinds of heat exchangers a satisfactory efficiency isachieved, however, as a result of the horizontal extension of thecolumns difficulties are encountered with regard to an efficientconcentrated withdrawal of the separated humidity or impurities,respectively, as well as with regard to a suitable guidance of the gasor refrigerant flow because the force of gravity does not act upon thegas or refrigerant flow in the flow direction but rather in a directiontransverse thereto.

It is known in the prior art to provide a device for separating humidityfrom wet gases or vapors wherein the gas flow to be cooled orrefrigerated is guided through two cooling chambers in a verticaldirection. Both chambers are connected in series and cooled by a commoncoolant flow. The gas to be cooled is passed through the first coolingchamber in a downward direction whereas it passes the second coolingchamber in an upward direction. Thus, the separated liquid, under theinfluence of the force of gravity, travels to the lower end of thecooling chambers from where the liquid may be readily withdrawn.However, the two prior art cooling chambers both are designed asgas/refrigerant heat exchangers whereas a gas/gas heat exchanger is not'present so that the overall efficiency is kept at a relatively lowlevel.

Another known device differs from the abovedescribed prior art merelyinsofar as both cooling chambers are not disposed beside each other butone above the other so that substantially the same functional operationsoccur except for the considerably larger height of construction which inmany cases may even be excessive.

It is an object of the present invention to improve such prior artdevices for achieving both an efficient withdrawal of the condensatealong with a suitable conduct of the gas and refrigerant flow andsimultaneously a good efficiency with respect to the cooling of the gasto be dried.

SUMMARY OF THE INVENTION The foregoing and other objects are achieved byan equipment arrangement which advantageously positions both a gas/gasheat exchanger and a gas/refrigerant heat exchanger in verticaldirection adjacent each other.

Due to such a structure and configuration of the device according tothis invention the desired goal is reached, namely, that the height ofthe construction is low and the condensate accumulates in a concentratedarea with the assistance of the force of gravity and, moreover, that theentire device exhibits a high cooling efficiency due to the refeeding ofthe gas cooled within the gas/refrigerant heat exchanger into the gas/gas heat exchanger.

In accordance with the illustrative embodiment of this invention, a gasto be dried is processed vertically downward from an upper inlet to alower outlet through a heat exchanger insert of a gas/gas heat exchangerdevice. The latter insert includes a plurality of pipes alignedvertically one above the other and in the downward path of the gas to bedried. Each of the pipes illustratively comprises a hollow inner portionextending longitudinally and in a horizontal plane with the insert. Eachof the pipes supports cooling fins, or ribs, for cooling gas includingthe gas from the inlet. Advantageously, the hollow portion of selectedones of the pipes communicate with another inlet of the gas/gas heatexchanger for recirculating gas cooled by a gas/refrigerant heatexchanger through the gas/gas heat exchanger for precooling newlyadmitted gas to be dried and for upward against the force of gravityexhausting the cooled, or dried, gas to the exterior of the gas/gas heatexchanger for function use.

A gas/refrigerant heat exchanger is used for further cooling of gasreceived from the lower outlet of the gas/gas heat exchanger and thencoupling the cooled gas through an impurities and separated liquidfilter to the hollow portion of the pipes in the gas/gas heat exchanger.The gas/refrigerant heat exchanger also comprises an insert comprising acooling coil network arrangement disposed in a vertically downward pathof the gas flow from the gas/gas heat exchanger via an upper inlet and alower outlet of the gas/refrigerant heat exchanger. The latter outlet iscoupled to the filter for communicating the cooled gas thereto forremoval of impurities.

In summary, the present invention provides for the flow of a gas to bedried in a vertically downward direction through a precooling gas/gasheat exchanger and thence in a vertically downward direction through arefrigerant cooling coil configurations of a gas/refrigerant heatexchanger for cooling. The processing continues by communicating thecooled gas through a filter for impurity removal and then byrecirculating the purified cooled gas through a pipe arrangement of thegas/gas heat exchanger. Such recirculation enables the cooled gas toprecool newly admitted gas within the gas/gas heat exchanger and therebyto increase the temperature of the cooled gas by a prescribed magnitudebefore it is exhausted from the gas/gas heat exchanger for functionaluse.

DESCRIPTION OF THE DRAWING The foregoing objects, features andadvantages, as well as others of this invention, may become more clearlyunderstood by a reading of the following description of an exemplaryembodiment thereof as shown in the accompanying drawing in which:

FIG. 1 is a side view, partially in section, of a device for drying gasby refrigeration;

FIG. 2 is a horizontal cross-section through the gas/- gas heatexchanger of FIG. 1, taken along line IIII;

FIG. 3 is a horizontal cross-section through the refrigerant/gas heatexchanger of FIG. 1 taken along line III-III;

FIG. 4 is a side view, partially in section, of an insert for therefrigerant/gas heat exchanger according to another embodiment of theinvention; and

DETAILED DESCRIPTION Referring now to FIG. 1, there is illustrated arefrigerating dryer according to one embodiment of this invention havinga vertically extending gas/gas heat exchanger 12 as well as agas/refrigerant heat exchanger 14 extending in parallel thereto.

The gas/gas heat exchanger 12 includes a cylindrical housing 16enclosing a heat exchanger insert 18 of rectangular cross-section.Collars 20 are secured to the outer circumference of the insert 18 bymeans of which the insert 18 rests upon brackets 22 fastened to theinterior surface of housing 16. As apparent in particular from FIG. 2,pipes 24 supporting cooling ribs 26 extend between two opposite sides ofthe insert 18 parallel above and besides each other.

At the upper end of the gas/gas heat exchanger 12 there is a stud-likeinlet 28 through which the gas to be dried, preferably air, may enter.This gas is passed through the insert 18 in the direction indicated byarrow m, thereby flowing through the hollow spaces defined between pipes24 and cooling ribs 26, respectively. From the lower end of the insert18, the gas to be dried is passed on to a studlike outlet 30 throughwhich it may escape from the gas/gas heat exchanger 12 as indicated withthe S-shaped dashed line leading from outlet 30 to asubsequent inlet 40of the gas/refrigerant heat exchanger 14.

Cooled gas as derived from the gas/refrigerant heat exchanger 14--thestructure of which is explained in greater detail hereafter-is refed viaa stud-like inlet 32 into the gas/gas heat exchanger 12 whereupon itenters the opposite free openings of pipes 24. The collar 20 adjacentinlet 32 prevents gas entering through inlet 32 from being applied tothe whole group of pipes 24 simultaneously. Rather, merely those pipes24 extending below the collar 20 adjacent inlet 32 are available toreceive gas. Through this lower portion of pipes 24 the gas travels tothe right side of the insert 18, in order to rise there to a maximumheight determined by the collar 20 located at this side of insert 18,and to enter further pipes (not shown) corresponding to pipes 24 so thatthe gas flow is conducted through pipes 24 in an S-like configuration.The open ends of the upper pipes 24 communicate with a stud-like outlet34 through which the dried gas may leave the refrigerating dryer 10. Inthe described embodiment according to FIG. 1, the gas flow is deviatedtwice, however, principally any other higher number of deviations maytake place.

Gas/refrigerant heat exchanger 14 includes a heat exchanger insert 36enclosed by a housing 38. Through the stud-like inlet 40 the gassupplied from gas/gas heat exchanger 12 may enter into thegas/refrigerant heat exchanger 14 in order to leave same upon passage ofthe heat exchanger insert 36 through a stud-like outlet 42 communicatingwith the inlet 32 of gas/gas heat exchanger 12.

A cooling coil generally designated 44 and having linear tube-likesections 46 is distributed over the entire height and width of insert 36(cf. FIG. 3). Sections 46 traverse insert 36 in a similar manner aspipes 24 intersect insert 18, except that at their ends they areconnected to subsequent sections 46 through U- connections 48,respectively. To increase the cooling action, the sections 46 may besurrounded by cooling ribs 50 as is conventional in the art. Thebeginning of cooling coil 54 communicates with an injection conduit 52whereas the end of cooling coil 44 terminates in an exhaust conduit 54so that the coolant may be pumped through cooling coil 44 in acontinuous closed loop.

Between outlet 42 and inlet 32 a filter 56 may be interconnected whichthen advantageously is located at the coolest point of the gas flow tobe dried and which thus may intercept separated liquid and impurities ina particularly effective manner.

The bottoms of the two heat exchangers may be provided with outlets 57and 58, respectively, through which the liquid separated from the gasflow may be readily withdrawn as under the influence of the force ofgravity it accumulates in the bottom area of the two heat exchangers andthus concentrates close to the two outlets 57 and 58, respectively.

Accordingly, the refrigerant dryer 10 according to this inventionprovides for a suitable withdrawal of the separated impurities and for asuitable course of the gas flow because it will always descend fromwarmer to cooler points and rises from cooler to warmer points,respectively. It also simultaneously guarantees good efficiency inasmuchas the cooled gas rising within the gas/gas heat exchanger 12 pre-coolsthe gas descending through insert 18 in direction of arrow m while thegas returning to outlet 34 through pipes 24 is pre-heated by thedescending gas fiow thus having resumed a desired relatively hightemperature level when exiting through outlet 34. In practice, thetemperature distribution may be such that the entering gas is at atemperature of 35 C, whereas it leaves gas/ gas heat exchanger 12 at atemperature of about 20 C. Upon travel through insert 36 the gas flowmay be at a temperature level of +2 C and that temperature may have beenincreased up to +25 C when the gas leaves gas/gas heat exchanger 12.

FIG. 4 shows a particularly advantageous embodiment of a heat exchangerinsert of this invention having a structure differing from that of heatexchanger insert 36 of FIG. 1. This insert likewise exhibits a case 60receiving cooling coil elements 62, 64 of substantially slice-likeconfiguration and having cooling coil sections 66, 68 At their lowerends the individual slice-like cooling coil elements 62, 64 rest uponsupports 70. At their ends, cooling coil elements 62, 64 terminate intoU-bows 72 by means of which they communicate with a manifold 74connecting cooling coil elements 62, 64 in parallel.

As evident from FIG. 4, each slice-like cooling coil element 62, 64comprises a plurality of cooling coil sections 66, 68 bent backwards andforwards in S-shaped' Cooling coil elements 62, 64 adjacent each othermay thus be interlaced with each other in a comb-like manner, so that amaximum filling factor for the volume is secured and immediatelyadjacent sections 66, 68 of neighboring cooling coil elements 62, 64

. may support each other mutually, thereby providing for a highmechanical stability of the entire cooling coil system. The mutualassociation of the sections of the cooling coil elements or of thecooling coil elements themselves is clearly illustrated in the lowerportion of FIG. 5.

It will thus be possible to bend the individual cooling coil elements62, 64 from one coherent tube so that it will be unnecessary to useseparate additional connecting members at the points of return as thishad been set forth in connection with FIG. 3. As will be understood thatthis kind of construction will yield a material cost saving becausesoldering or brazing operations are not required any more. Beyond that,reliability will be increased because leakages due to imperfactsoldering work are impossible. Moreover it is warranted that theindividual cooling coil elements do not exhibit any regions in which therefrigerant would have to flow in an upward direction. This avoids thatimpurities contained in the refrigerant such as oil which might separatein the course of the passage of the refrigerant through the cooling coilelements might settle within the cooling coil system. Rather, as thesections 66, 68 are continuously extending in a downward directionthroughout any danger of a possible accumulation of impurities within acooling coil element is removed. While refrigerants are available forwhich the occurrence of oil or other residues do not necessarily have anadverse effect, such refrigerants exhibit but a comparatively lowcooling capacity.

While almost any hollow spaces between adjacent sections bent in azig-zag-like manner and belonging to one cooling coil element are filledby corresponding neighboring sections, free hollow spaces remain betweenadjacent sections of the two outer cooling coil elements through whichthe gas to be dried might flow without sufficiently intensive contactwith the cooling coil system.

Therefore, into at least a part of these hollow spaces baffles 86 mayproject which extend substantially over the entire length of sections66, 68 and are fastened to the adjacent wall of case 60. These baffles86 assure a close contact of the gas current with the cooling coilelements in the area of the outer hollow spaces, too.

In order to further enhance the rigidity of the system formed by coolingcoil elements 62, 64, contiguous sections of adjacent cooling coilelements may be connected with each other for example by brazing, inparticular in the point of return area. Similarly, the outer coolingcoil elements may be affixed to case 60.

The refrigerating dryer according to this invention may be used forquantities on an order of magnitude of 3,000 m. The three majorcomponents of the refrigerating dryer, namely the gas/gas heatexchanger, the gas/refrigerant heat exchanger and the heat exchangerinsert may be designed as modules which may be composed due to theprevailing operation conditions with regard to the amount of gas (air)to be conveyed and the desired temperatures, or which may be replaced bysuitable larger or smaller similar modules when there is a change in theoperation conditions.

What is claimed is:

1. In an apparatus for drying gas, in particular air, by refrigeration,including a gas/gas heat exchange and a gas/refrigerant heat exchanger,said exchangers extending with their longitudinal axes in a verticaldirection, a heat exchanger insert for at least said gas/refrigerantexchanger, said heat exchanger insert comprising a plurality of coolingcoil elements being connected in parallel and combined into a closedpackage and having a plurality of cooling coil sections being bent intheir longitudinal direction backwards and forwards in an S-likeconfiguration and extending in a horizontal direction substantially inparallel, said sections further alternating with regard to thecross-section of a cooling coil element in a zig-zag manner between afirst and a second plane, adjacent cooling coil elements meshing witheach other so that immediately neighboring sections of adjacent coolingcoil elements provide for a mutual support.

2. An apparatus as defined in claim 1 wherein said immediatelyneighboring sections of adjacent ones of said cooling coil elements arerigidly connected with each other.

3. An apparatus as defined in claim 2 wherein baffles are accommodatedin free hollow spaces between neighboring sections of said cooling coilelements positioned at the outer sides of said cooling coil package,said baffles extending substantially over the entire length of a coolingcoil section.

4. An apparatus as defined in claim 3 wherein any of said heatexchangers is equipped with a heat exchanger insert and wherein saidgas/gas heat exchanger, said gas/refrigerant heat exchanger and/or saidheat exchanger insert each are constructed as modules replaceableindependently of each other.

1. In an apparatus for drying gas, in particular air, by refrigeration,including a gas/gas heat exchange and a gas/refrigerant heat exchanger,said exchangers extending with their longitudinal axes in a verticaldirection, a heat exchanger insert for at least said gas/refrigerantexchanger, said heat exchanger insert comprising a plurality of coolingcoil elements being connected in parallel and combined into a closedpackage and having a plurality of cooling coil sections being bent intheir longitudinal direction backwards and forwards in an S-likeconfiguration and extending in a horizontal direction substantially inparallel, said sections further alternating with regard to thecross-section of a cooling coil element in a zigzag manner between afirst and a second plane, adjacent cooling coil elements meshing witheach other so that immediately neighboring sections of adjacent coolingcoil elements provide for a mutual support.
 2. An apparatus as definedin claim 1 wherein said immediately neighboring sections of adjacentones of said cooling coil elements are rigidly connected with eachother.
 3. An apparatus as defined in claim 2 wherein baffles areaccommodated in free hollow spaces between neighboring sections of saidcooling coil elements positioned at the outer sides of said cooling coilpackage, said baffles extending substantially over the entire length ofa cooling coil section.
 4. An apparatus as defined in claim 3 whereinaNy of said heat exchangers is equipped with a heat exchanger insert andwherein said gas/gas heat exchanger, said gas/refrigerant heat exchangerand/or said heat exchanger insert each are constructed as modulesreplaceable independently of each other.